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PostPosted: Sun 26 May 2013 14:21 
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Field Trip to Ingleton (study of Porcellanous Bed) - Saturday 6 July

This is the field meeting that was postponed from earlier this year. Apologies for the short notice, but there were a number of problems that have only just been ironed out.

The Significance of the Porcellanous Bed to Cave Formation in the Yorkshire Dales

The meeting will assemble at the Methodist Church in Ingleton at 9.30 am. (This is in the centre of Ingleton, close to the Three Horseshoes pub on Main Street). In the morning there will be a series of talks explaining what the Porcellanous limestone bed is, where it occurs and why it is important to cave formation in the Yorkshire Dales. After lunch the meeting will split into two groups to visit outcrops of the porcellanous bed in Kingsdale and in Crummack Dale. Following the field visits we will return to the church for a discussion. The meeting is expected to finish at about 6 pm. The meeting organiser is Dave Checkley, to whom further enquiries should be addressed. Dave’s contact details are at http://bcra.org.uk/contact.html#b.

Further information and programme

Getting to the Ingleton Methodist Church
When approaching Ingleton from the south, on the B6255 the church is on the right immediately after the Three Horseshoes. It should be possible to park in the pub car park but, if not, there is limited space outside the church itself and there is a pay and display car-park at the Ingleton Community Centre, which is 100m back towards the A65 (but note the one way system!).

There will be a charge of £4 per person for participation, with reductions for BCRA members. This charge will include tea and biscuits in the morning and afternoon, but you are advised to bring a packed lunch. For those who dont manage to bring food, there are several cafes, shops and pubs in Ingleton that sell food. Those going walking on the afternoon field visits will need boots and waterproofs.

Programme
  • 9.30 Dave Checkley. Introduction to BCRA and the Field Meeting with reference to the work of the late Dick Glover.
  • 9.45 Tony Waltham. Geological influences on the caves of the Yorkshire Dales. (See abstract below)
  • 10.15 Tea break
  • 10.45 Dave Lowe. The Porcellanous Bed – not so much a 'control', more of a 'signpost'. (See abstract below)
  • 11.15 Eric Johnson. Eric will talk about his work with the British Geological Survey to map the porcellanous bed in the Settle area in the 1970's
  • 11.45 Dave Brook. Dave will discuss the elusive Porcellanous bed's position at the S/D boundary in the great scar limestone and will question its role in guiding cave development in Gaping Gill and elsewhere.
  • 12.15 Discussion period
  • 12.45 Lunch Break
  • 13.30 Fields excursions. Two groups. 1) Kingsdale, 2) Crummack Dale
  • on return to Ingleton: discussion: Identify surface areas where the bed is not yet known or in dispute and try to get people to go and look for it.
    Identify areas underground where it has not been recorded, but ought to be there. Plan for a follow-up publication and or meeting.
  • 18.00 Finish

Geological influences on the caves of the Yorkshire Dales - Tony Waltham.
The Dales provide a prime example of geological influence, or even control, over the patterns of cave development. Though there are some classic exceptions, the morphology and even the origins of almost every cave passage in the Dales can be related to features of the limestone geology. The numerous shale beds are obvious influences, but their role is not always as simple as might first appear. There are also other influences within the stratigraphy, including those known as inception horizons and also that slightly mysterious bed of porcellanous affinity. And then there are the joints and faults, and yet more to debate. We know more about the geological factors than we did fifty years ago, but there is still much to understand.

The Porcellanous Bed – not so much a 'control', more of a 'signpost' - Dave Lowe
Caves are the explorable segments of an integrated underground drainage network that underpinned the development of the more visible surface karst landscape of the Yorkshire Dales. Caves and tributary conduits occur within and through some 180m of largely massive limestone beds now known as the Great Scar Limestone Group. Close to the middle of the Great Scar Limestone succession is the Porcellanous Bed, a widespread but thin (commonly 0.6 to 0.9m) marker horizon that can be traced at the surface, but is also recognizable in cave passages and shafts in parts of the district. Views about its origin, broader geological context, lateral ramifications and speleogenetic significance are still evolving. Controversy relating to its supposed local control of cave development has been overtaken by its subtly different interpretation as an inception horizon, guiding the earliest speleogenesis and acting more generally as one of several geological signposts that might point towards likely locations of elements of a primitive, potentially Dales-wide, imprint of bedding-related dissolutional voids. As in science generally, much depends on understanding the terminology used and its context, as well as a willingness to adopt a lateral viewpoint that extends beyond the obvious roles and relationships of accessible cave passages and penetrates towards the hidden roots of cave guidance.


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